As far as villains go he's among the best, quite easily. The deceptive looking frail old man who is actually an absurdly powerful being, with powers far beyond the good guys (atleast in the movies). He planned decades of manipulation, clouding the sight of literally hundreds of Jedi, including that of Grand Master Yoda. He also held his own against two of the strongest Jedi in battle; Mace Windu and Master Yoda.